Due to a mechanism not entirely understood, a person's cardiovascular blood delivery system often becomes less efficient as one ages. Although the causes of arterioscleroris are not completely understood, one symptom is the partial or, in extreme cases, the total blockage of a blood vessel due to a build up of deposits along an inner surface of the blood vessel. The increase in the number of coronary by-pass operations is some indication of the incidence with which the problem is encountered in older patients.
Prior art proposals recognize that one possible procedure for treating a condition of partially or totally blocked blood vessels is to open the blocked blood vessel. One such prior art technique for reopening a blocked blood vessel is to insert a balloon catheter within the vessel to expand the vessel and either break loose deposits within the vessel or alternatively, increase the size of the lumen passing through those deposits.
An alternate proposal for opening a blocked vessel is to bring a high-speed rotating device into contact with occluded portions of the blood vessel. The rotating device produces cutting, abrading, or fluid turbulence to open the vessel and increase blood flow. One device for physically opening the blood vessel in this manner is disclosed in U.S. Pat. No. 3,762,416 to Moss entitled "Improvements In or Relating To Drills for Clearing Obstructions". In this patent, a high-speed motor rotates a flexible drive shaft connected to a cutting bit. The bit and flexible drive shaft are inserted into an occluded blood vessel so that when the bit is rotated at high speed and moved into contact with occluded regions it breaks loose deposits within the blood vessel.
A more recent prior art patent disclosing a similar system for blood vessel cannulization is disclosed in U.S. Pat. No. 4,445,509 to Auth entitled "Method and Apparatus for Removal of Enclosed Abnormal Deposits". This patent describes a differential cutting tool mounted at the end of a flexible shaft which can be inserted into an occluded blood vessel. Again, high speed rotation of the cutting tool causes the tool to remove abnormal deposits from inside the blood vessel.
U.S. Pat. No. 4,589,412 to Kensey entitled "Method and Apparatus for Surgically Removing Remote Deposits" discloses a procedure for removing atherosclerotic plaque. A cutting tip is rotated by the application of fluid pressure through a multi-lumen catheter.
The systems disclosed in these prior art patents include a flexible catheter having an integral rotable cutting tool for removing material within an occluded blood vessel. When the physician inserts the catheters disclosed in these prior art patents an obstructed or partially occluded blood vessel has most probably already been identified using a conventional angiographic catheter and angiographic imaging techniques. The angiographic catheter is withdrawn and one of the dedicated catheters re-inserted for treatment of the vessel obstruction.
A typical prior art angiographic system includes a metering pump for delivering an opaque dye to an angiographic catheter that has been inserted into the patient. The metering pump delivers the opaque dye at a controlled rate as the physician monitors a viewing screen to observe the internal structure of the patient. During this procedure, occluded regions of a patient's blood vessel can be identified. The angiographic catheter is then removed. One of the special catheters having an integral rotating head at its distal end might then be re-inserted to position the rotatable head in proximity with the occluded region to cannulize or open the blocked vessel.
A number of patents disclose prior art angiographic catheters. U.S. Pat. No. 3,503,385 entitled "Guidable Catheter Assembly and Manipulator Therefore", U.S. Pat. No. 3,485,234 entitled "Tubular Products and Method of Making Same", and U.S. Pat. No. 3,585,707 entitled "Method of Making Tubular Products" are representative prior art patents relating to angiographic catheters. These three patents are assigned to the assignee of the present invention and are incorporated herein by reference.
Due to the construction of the catheters disclosed in the aforementioned prior art patents to Moss, Auth and Kensey, it is anticipated the process of re-inserting the second catheter, routing it to the occluded region of the vessel and cannulizing the vessel may be difficult, especially for small diameter vessels. Indeed, it may be that the catheters proposed in these prior art patents are larger in diameter than the vessel that needs cannulization.